Chromosome number ofSaruma oliver (Aristolochiaceae)

Chromosome number ofSaruma henryi, the only species of the genus, was counted for the first time. The species has 2n=52 chromosomes, and its chromosomal complement is characteristically composed of very small chromosomes. Based on chromosome data available for the family, comparisons indicate an isolated position ofSaruma in Aristolochiaceae.     

Chromosome number of theOxalis tuberosa alliance (Oxalidaceae)

Twelve taxa of theOxalis tuberosa alliance were analysed and found to share the same basic chromosome number x = 8. The karyotypes are composed by small metacentric and submetacentric chromosomes. Different ploidy levels were found among the taxa: there were 9 diploids, 1 tetraploid, 1 hexaploid and 1 octoploid. The last ploidy level corresponds toO. tuberosa, the only tuber bearing taxon found so far in the alliance. Cytotaxonomic evidence and evolutionary considerations suggest to classify theO. tuberosa alliance in sect.Herrerea.     

Isozyme variation in Larrea ameghinoi and Larrea nitida (Zygophyllaceae): genetic diversity and its bearing on their relationship

Electrophoretic variants for 11 isozyme systems were examined by horizontal polyacrilamide gel electrophoresis in natural populations of Larrea ameghinoi and L. nitida (section Larrea). The two taxa presented fixed alternative allelic variants at loci Adh-1, Gdh-1 and Mdh-1. Genetic variability estimates showed no statistically significant differences among populations of section Larrea (H_e: 0.097–0.167). However, these values were significantly lower than those reported for species of section Bifolium (L. divaricata, diploid L. tridentata) in a previous contribution (H_e: 0.17–0.29). Positive and highly significant Wright's fixation indices are in agreement with higher amounts of inbreeding for nitida and L. ameghinoi, as suggested on the basis of floral morphology by previous authors. Moreover, the higher levels of genetic differentiation obtained for conspecific populations of section Larrea as compared to those of section Bifolium are also consistent with these observations. Nei's genetic identity values obtained for sympatric (I=0.80) and allopatric (I=0.63–0.73) L. ameghinoi – L. nitida population pairs are concordant with those expected for different, but closely related congeneric species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Chromosome number evolution in the tribeBrassiceae (Brassicaceae): Evidence from isozyme number

Variation in isozyme number was used to assess the evolution of haploid chromosome numbers (n=6–75) and systematic relationships in the tribeBrassiceae, which is believed to be one of the few monophyletic tribes in theBrassicaceae. Ten enzyme systems were surveyed among 108 species in 35 genera of tribeBrassiceae and for 11 species from seven other tribes. The data indicated that taxa with n=7–13 and n=14–18 were similar in isozyme number, suggesting that genera with n=14–18 did not arise from polyploidy (i.e. entire duplication) of the n=7–13 genomes. These results suggest that aneuploidy and/or chromosome fusion/splitting have played a more significant role than polyploidy in the evolution of higher base chromosome numbers in the tribe. The detection of widespread isozyme duplication in the tribe is consistent with reports of extensive gene duplication in theBrassica crop species, and suggests that the common ancestor of the tribe already had undergone a polyploid event, i.e. complete genome duplication, prior to aneuploid divergence. Inheritance studies conducted onSinapis arvensis showed that segregation ratios at seven loci (Fbp-2,Gpi-2,Idh-2,Pgm-2,Pgm-2,Tpi-1,Tpi-1) conformed to those expected under Mendelian inheritance. Isozyme duplications were phylogenetically informative at various taxonomic levels in the tribe. In particular, duplications for cytosolic phosphoglucomutase (Pgm-2,Pgm-2) and plastid triosephosphate isomerase (Tpi-1,Tpi-1) were evident in 33 of the 35 genera examined, supporting the monophyletic status of theBrassiceae with the inclusion ofOrychophragmus and the exclusion of controversial membersCalepina andConringia.     

Chromosome counts inCephalotus (Cephalotaceae)

Cephalotus follicularis is uniformly n = 10 in all populations surveyed.     

Chromosome evolution in Himalayan Impatiens (Balsaminaceae)

AKIYAMA, S., WAKABAYASHI, M. & OHBA, H., 1992. Chromosome evolution in Himalayan Impatiens (Balsaminaceae). Chromosome numbers and karyotypes have been investigated in species of Himalayan Impatiens . In addition to confirming previous chromosome counts, the presence of a tetraploid taxon ( I. exilis) is revealed. In central and east Nepal species with x = 9 are more common than those with other basic numbers and this number is shown to be one of the most frequent numbers in the genus. Most species with x = 9 have a bimodal karyotype. The species relationships are discussed.     

Chromosome cytology and karyotype change inGalaxia (Iridaceae)

Basic chromosome number inGalaxia is believed to be x = 9, and this number, or multiples, occurs in all species of subgenusGalaxia. In subgenusEurystigma, G. barnardii has n = 8,G. versicolor n = 8 and 7,G. citrina n = 8, 7 and 17 whileG. variabilis has n = 7 exclusively. Karyotypes in forms ofG. versicolor with n = 7 and inG. variabilis are quite different and clearly originated independently. Karyotypic features provide evidence for the hypothesis that changes in chromosome number were accomplished through chromosome fusion either by classical Robertsonian translocation, or unequal reciprocal translocation.     

Chromosome numbers in the genus Lippia (Verbenaceae)

The genus Lippia (Verbenaceae) comprises about 200 taxa mainly distributed in Brazil, Mexico, Central America, Africa, Argentina and Paraguay. Some problems involving the number and delimitation of species have been reported. In order to contribute to the solving of these problems, the chromosome numbers of 14 Lippia species are documented. The following species were collected at Espinhaço Range, Southeast Brazil: Section Zapania (L. corymbosa, L. diamantinensis, L. hermannioides, L. lacunosa, L. rotundifolia, L. rubella), section Rhodolippia (L. florida, L. lupulina, L. pseudothea, L. rosella), section Goniostlachyum (L. glandulosa, L. pohliana, L. sidoides) and section Dioicolippia (L.filifolia). Immature inflorescences were collected and the ideal size for chromosome observation was determined. The majority of species have a haploid chromosome number from 10 to 14. Few species have a higher chromosome number, which suggests the occurrence of polyploidy. The relationships between chromosome numbers and the taxonomic sections are also discussed.     

Chromosome banding patterns of the aye-aye,Daubentonia madagascariensis (primates,Daubentoniidae)

The aye-aye (Daubentonia madagascariensis) is an endangered prosimian primate found only on the island of Madagascar. It is the only extant representative of its family Daubentoniidae. The phylogenetic relationship of this species with other prosimians is unclear. Because a G-banded karyotype forDaubentonia has not previously been reported, blood for preparation of lymphocyte cultures was obtained from one of the four aye-ayes in captivity in the United States. The diploid chromosome number was 30. The karyotype consisted of 14 autosomal metacentrics, 10 autosomal submetacentrics, and 4 autosomal acrocentrics. The similarities between the G-banded chromosomes ofDaubentonia and those ofPropithecus, a member of the Indriidae, support the notion thatDaubentonia has a closer relationship with the Indriidae than with other Lemuriformes or the lorisoids.     

A new low chromosome number forOrnithogalum tenuifolium (Hyacinthaceae)

A new chromosome number (2n=4) forOrnithogalum tenuifolium Delaroche is reported. The new chromosome race is postulated to have originated by a Robertsonian translocation from a Southern African chromosome race with six chromosomes, and represents thus the final step in a series of decreasing basic number of the species.     

3种香薷属植物染色体数目与核型分析

参照植物根尖细胞学研究的方法标准,对香薷属3种(5个居群)植物进行核形态学分析。结果表明:(1)从染色体数目看,密花香薷2居群染色体数目2n=16;野苏子2居群染色体数目2n=20,染色体数目和倍性与前人报道的一致;毛穗香薷染色体数目2n=10为首次报道。(2)聚类分析结果显示,3种(5居群)植物中野苏子和密花香薷亲缘关系较近;结合现有报道数据分析表明,该属植物仅有2种倍性(二倍体和四倍体),且二倍体占主导地位。(3)核型参数分析表明:密花香薷的稻城无名山居群1核型公式为2n=2x=16=14m+2sm,居群2为2n=2x=16=16m,着丝粒指数(CI)分别为39.57和42.32,不对称系数AI值分别为2.75和2.87,核型不对称性都为1A型;毛穗香薷的核型公式为2n=2x=10=10m,着丝粒指数(CI)为41.76,不对称系数AI值为5.25,核型不对称性为1B型;野苏子的昆明西山居群核型公式为2n=2x=20=14m+6sm,聂拉木樟木沟居群为2n=2x=20=16m+4sm,着丝粒指数(CI)分别为38.49和40.97,不对称系数AI值为4.20和4.30,核型不对称性为1B型和2B型。     

Chromosome number,morphology, pairing,and DNA values of species and hybrids in the genusFallopia (Polygonaceae)

The taxa in this study have in the past been treated together in sect.Tiniaria Meissner ofPolygonum L. s.l., and more recently the large erect rhizomatous herbaceous perennials have been separated from the twining annuals and perennials as the generaReynoutria andFallopia respectively. These taxa range in ploidy level from diploid to octoploid, with base numbers of both 10 and 11 present. The plants are primarily Asiatic in distribution, although many of the large erect perennials are now naturalized in many parts of Europe. Cytological examination has revealed the presence of a number of previously unknown hybrid taxa in the British Isles. The readiness with which hybridisation occurs between taxa of differing base number and ploidy level, and similarities revealed in chromosome morphology, meiotic pairing and in DNA C-value, suggest to the authors that these two genera are best amalgamated underFallopia.     

Chromosome number and karyotype of Phaenospermateae and Duthieeae (Poaceae), with reference to their systematic implications

Recent molecular phylogenetic studies indicate that Phaenospermateae and Duthieeae are among the early diverging lineages of Pooideae and that they are closely related to each other. Here, we test this with cytotaxonomical data. The monotypic tribe Phaenospermateae, represented by Phaenosperma globosum, has a chromosome number of 2n = 2x = 24 and a fairly symmetric karyotype consisting of 22 median (m) and 2 submedian (sm) chromosomes varying in length between 1.8–3 μm. Duthieeae, represented by Duthiea brachypodium, Sinochasea trigyna, Stephanachne monandra and Stephanachne pappophorea, also share the chromosome number 2n = 2x = 24 and similar symmetric karyotypes with the chromosomes varying in length between 1.4–5 μm. Thus, the close relationship of Phaenospermateae and Duthieeae is corroborated.     

The chromosomes ofGrahamia (Portulacaceae)

The somatic and gametic chromosomes of the monotypical genusGrahamia (G. bracteata) have been studied for the first time: 2n = 18, n = 9. The karyotype is symmetrical; of the nine m pairs one has microsatellites. The basic chromosome number x = 9 is considered to be primitive within the family.     

Chromosome counts inPosidonia (Posidoniaceae)

The five species ofPosidonia occuring in Western Australia all have a diploid chromosome number of 20.     

New chromosome number inRutaceae

Detailed chromosome counts have been made in 61 species, belonging to 33 genera ofRutaceae. 30 of these species are reported here for the first time. For 18 species at least one previous publication gives a chromosome number differing from that reported here. Such discrepancies are, in most cases, due to errors in counting or identification of the material. By critically reviewing the literature on each particular case, it appears possible to eliminate most of the false data. On the basis of the present results, the base number x = 10 is proposed for the genusRuta. Cytogenetics ofRutaceae, I.     

Chromosome counts inCalea (Asteraceae-Heliantheae)

Chromosome numbers are reported for six taxa ofCalea, among them tetraploidC. septuplinervia, the only known polyploid inCalea s. str. The base chromosome number ofCalea is interpreted as x = 19.     

Chromosome analysis ofHaemanthus andScadoxus (Amaryllidaceae)

Chromosome analysis of nine species ofHaemanthus (2n = 16) and four species ofScadoxus (2n = 18), using conventional stains, Quinacrine fluorescence and C-banding, has shown that the two genera do not possess significant amounts of constitutive heterochromatin. The two genera are closely related and differ in respect of a translocation which has resulted in the dysploid reduction in chromosome number from 2n = 18 inScadoxus to 2n = 16 inHaemanthus.     

不同产地木耳菜的染色体核型分析

为了研究木耳菜核型特征及不同产地间的进化关系,以来自7个产地的8个木耳菜品种为材料,采用常规压片法进行核型分析,并进行核型进化趋势分析和主成分分析。结果表明:(1)所有木耳菜的染色体数目均为2n=2x=44,未见异常染色体,染色体类型均为中部着丝粒染色体(m)或近中部着丝粒染色体(sm),且m数量多于sm。(2)不同产地的木耳菜在染色体核型公式、核型类型、随体位置、染色体长度比、臂比及核型不对称系数等指标均存在明显差异;随体均为1对,但随体位置不同。(3)核型类型为1A、1B和2A型,其中1A型5种,数量最多。(4)染色体长度比范围为1.51~2.06,平均臂比值范围为1.30~1.48,仅有吉林‘利丰’和江西‘航城’存在臂比大于2的染色体。(5)核型不对称系数范围为56.25%~59.17%,核型的对称程度较高,推测木耳菜的进化程度较为原始,其中河北‘金发’是最原始,江西‘航城’最进化。研究结果为木耳菜的细胞遗传学研究提供了参考依据。